MD22l timing belt deflection

[mibbal]

Hello All,

I'm going to change timing belt on my MD22L 2001 since I have no idea is it was ever changed... I've already bought the belt, idler and tensioner, and studied service manual for the procedure.

The problem is tensioning... Manual mentions the correct value for a new belt is 425-465 N and for a used belt 340-370 N. But this is with standard gauge I do not have and which is quite expensive https://www.ebay.com/itm/116043453574?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=V3l2CAKkSb2&sssrc=2047675&ssuid=fyGmBEiUSdW&widget_ver=artemis&media=COPY)

There are much more cheap tools like this one https://www.ebay.com/itm/355281967981?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=ehsaeg2xrqo&sssrc=2047675&ssuid=fyGmBEiUSdW&widget_ver=artemis&media=COPY, but for this tool you need to know belt deflection with specific force applied.

I spent several days searching for belt deflection for MD22/Perkins but was not able to find this info.

Does anyone know this? Or any other suggestion on timing belt tension apart from buying an expensive gauge?

Thank you in advance!

[IslandAlchemy]

When the belt is on, if you get hold of it between the two top gears, you want to be able to twist it 45 degrees. That will be the right tension.

[mibbal]

When the belt is on, if you get hold of it between the two top gears, you want to be able to twist it 45 degrees. That will be the right tension.

Thanks, IslandAlchemy

45 or 90 degrees?

[Yngmar]

You can also check belt tension by plinking it like a guitar string and checking the frequency it vibrates at. Need to measure the length over which it can swing freely and weigh the new belt before installation (total length is on the packaging). That gives you the frequency to tune the belt to. A guitar tuning app on the phone is sufficient.

That's how I did it and it worked well. Can't find my notes with the calculation now, but that's how they do it in industrial and automotive applications too.

The twist method is ok for a basic sanity check, but very inaccurate.

[sy_Anniina]

I have been wondering about belt tension measurement as well - changing our belt has been on the long list of "maybe this year" jobs. I feel embarrassed as an old physicist not having thought about the frequency method 

Just FYI - found an online frequency calculator that will give you the frequency once you have the relative input data Yngmar stated above. https://www.clavis.co.uk/belt-calculator/

BR,

Tommi - s/y Anniina

[mibbal]

Whauu! That's amazing. Thanks a lot for the idea and formulas, will proceed this way!

[IslandAlchemy]

When the belt is on, if you get hold of it between the two top gears, you want to be able to twist it 45 degrees. That will be the right tension.

Thanks, IslandAlchemy

45 or 90 degrees?

45 degrees either way.

[chowder]

I changed our timing belt and the tension spec was too much. I found that the cam and flywheel alignment holes were off enough that one, or the other, but not both alignment holes weren't in line (very close though). Ensuring that the cam was not off a tooth either direction, I tensioned the belt so both cam and flywheel holes lined up. Whatever tension spec that is really doesn't matter too much, so long as the fuel pump is correct as well. Re-check belt tension after running an hour or two then again until you're comfortable with your work. Then, check the alignment holes and "general tension" (aka finger) at least annually.

The MD22L has never run better since we've owned it.